全新java初学者实践教程6(Java SE5.0版)
iMYvC w/t6 基本语法3
e*:[#LJ]C a:7"F{D91 ,`B*rCOa 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
')}$v+9h 0A/GWSmF [font="Times] 1.循环语句[font="Times]:while,do-while,for
>pT92VN }Sqey:9jH [font="Times]2.分支语句[font="Times]:if-else,switch,
7f~DD8 R [font="Times]
Vt*Duh+4 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
t? yMuK [font="Times]
>dn[oS, 4.异常处理语句[font="Times]:try-catch-finally,throw
w' #VN|;;! I^ppEgYSY 实践:
3JWHyo [font="Times] 1.循环语句
L5]*ZCDv [font="Times] while 语句
6P3ezl@#; [font="Times]class While {
l92#F* [font="Times]public static void main(String args[]) {
'w^1re=R [font="Times]int n = 10;
{M$mrmG [font="Times]while(n > 0) {
LdDkd(k [font="Times]System.out.println("tick " + n);
DbH{;
Fb [font="Times]n--;
u3dh MnUn [font="Times]}
AW!|xA6'`: [font="Times]}
L_=J(H| [font="Times]}
2<qq[2 [font="Times] do…while 语句
(3&@c!E [font="Times] class DoWhile {
)p).}" [font="Times]public static void main(String args[]) {
N"2P&Ho] [font="Times]int n = 10;
hm&{l|u{RU [font="Times]do {
kS8srT
/H [font="Times]System.out.println("tick " + n);
vWXj6} [font="Times]n--;
sO~N2 [font="Times]} while(n > 0);
2sk^A
ly [font="Times]}
Cx}
Yp- [font="Times]}
oy;N3 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
_|g(BK2} [font="Times] for语句
Xa Yx avq [font="Times] class ForTick {
>OBuHqC [font="Times]public static void main(String args[]) {
U3&*,xeU@H [font="Times]int n;
I^qk` 5w [font="Times]for(n=10; n>0; n--)
/1gKc}rB2 [font="Times]System.out.println("tick " + n);
7=6p [font="Times]}
ec)G~?FH [font="Times]}
I,l%6oPa 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
D-8%lGS 还有啊,[font="Times]for循环的部分可以为空的
ouPwhB,bg [font="Times]class ForVar {
~i=/@;wRp [font="Times]public static void main(String args[]) {
Q{0-pHr} [font="Times]int i;
ZL+{?1&- [font="Times]boolean done = false;
Wu2#r\
[font="Times]i = 0;
T=A7f6` [font="Times]for( ; !done; ) {
LrsP4G [font="Times]System.out.println("i is " + i);
7?]gUrE [font="Times]if(i == 10) done = true;
jcYI"f"~ [font="Times]i++;
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n5;fp [font="Times]}
[64K?l0& [font="Times]}
C;OU2,c,T [font="Times]}
循环语句的例子下载 tv,^ Q} [font="Times] 2.分支语句[font="Times]
YL;ZZ2A [font="Times] if/else语句
@lc1Ipfk" [font="Times]class IfElse {
X.o[=E [font="Times]public static void main(String args[]) {
nsaf6y&E [font="Times]int month = 4; // April
qWy{{A+ [font="Times]String season;
CDO_A \ [font="Times]if(month == 12 || month == 1 || month == 2)
MVe5j+8 [font="Times]season = "Winter";
!,V8?3.aJn [font="Times]else if(month == 3 || month == 4 || month == 5)
AA^3P?iD
[font="Times]season = "Spring";
QtW5;A-h [font="Times]else if(month == 6 || month == 7 || month == 8)
/ZvNgaH5M [font="Times]season = "Summer";
hOO)0IrIM* [font="Times]else if(month == 9 || month == 10 || month == 11)
Z5bmqhDo[ [font="Times]season = "Autumn";
@ J!)o d [font="Times]else
Y~,[9:SR [font="Times]season = "Bogus Month";
XqyfeY5t [font="Times]System.out.println("April is in the " + season + ".");
VCX})sp [font="Times]}
0d9rJv}~ [font="Times]}
WvAl!^{` [font="Times]//这段程序输出[font="Times]:
23U9+ [font="Times]//April is in the Spring.
BYhPOg[ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
$*MjNj2 [font="Times] switch语句
Y=vA;BE]R [font="Times] class Switch {
jSa EwN [font="Times]public static void main(String args[]) {
/:z}WAW [font="Times]int month = 4;
7 G~MqnO| [font="Times]String season;
!:c7I@ [font="Times]switch (month) {
"sUe:F; [font="Times]case 12:
VS%8f.7ep [font="Times]case 1:
h7~&rWb [font="Times]case 2:
l9qq;hhGP, [font="Times]season = "Winter";
dGQy=T: [font="Times]break;
VrQw;-rQ [font="Times]case 3:
Wa2V Z [font="Times]case 4:
$kZ,uvKN [font="Times]case 5:
:c!7rh7O [font="Times]season = "Spring";
kD >|e<}\ [font="Times]break;
SdnqM`uFo [font="Times]case 6:
aS'G&(_ [font="Times]case 7:
DJr 8<u [font="Times]case 8:
"P&|e|7 [font="Times]season = "Summer";
~N>[7I"* [font="Times]break;
3-hu'xSU [font="Times]case 9:
G"O%u|7 [font="Times]case 10:
$QNfy.6Tn [font="Times]case 11:
.^,fw=T|1 [font="Times]season = "Autumn";
6$%]p1"!K [font="Times]break;
jQ%}e" [font="Times]default:
!r.X. C [font="Times]season = "Bogus Month";
cd)<t8^KE [font="Times]}
(xG#D;M0 [font="Times]System.out.println("April is in the " + season + ".");
w^A8ZT0^7 [font="Times]}
|jEKUTv,G [font="Times]}
分支语句代码下载 DS=kSkW^&5 ~ Y4H)r [font="Times]switch语句适合于条件非常多的逻辑
h:a5FK@ 请看上述语句可以混合使用,请看
下载例子